Swiss Pat. No. 632.895 corresponding to U.S. Pat. No. 4,430,009 discloses an arrangement, wherein a battery is maintained on the base plate by a clamp screwed on at its ends and located on the back cover side of the watch. There is inserted between the electrode of the battery and the clamp a printed circuit which includes a conductive track in contact with the electrode. The battery is housed in a hole which completely pierces the base plate, the rim of this hole on the dial side being provided with a flange in the form of a bevel projecting into the hole. In this arrangement the edge of the battery rests on the bevelled flange.
Such an arrangement enables reduction of the height required by the battery housing and presents an advantage over the proposal shown for instance in British Pat. No. 1.408.610. In this latter, effectively, the battery is housed in a hole provided in the base plate, the bottom of the hole being constituted by a wall forming part of said base plate. It is known that in order to be practically realizable, this bottom must have a thickness of at least 0.15 to 0.20 mm. There results therefrom a prohibitive space requirement in the sense of the thickness of the watch, particularly where watches of the so-called extra-thin variety are concerned.
The first of the cited documents presents however several disadvantages. Initially, the construction as proposed is poorly adapted to the extreme tolerances which are found in the diameter of the battery. If this diameter is small, there is a risk that the battery will not come to rest on the bevelled flange, but directly on the watch dial. Thence, if the battery should be introduced in the inverted sense, there is a substantial probability that its electrode will come into contact with the dial, thus creating via the base plate a short-circuit at the terminals of the battery. Finally, the clamp as proposed fixed by means of two screws to the base plate, does not permit absorbing the considerable differences which are met with in the thickness even of the batteries capable of being employed.